Vector G08 Series, Faq

Page: 9 / 42

G08 Vector Monitor Guide
Page 9 of 41
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R635 and R735: Some G08 deflection boards have a ‘teepee’ of large ceramic resistors in
these locations. As noted in the schematics, there should be a single 3-Ohm 20W resistor in
each location. Some have been replaced with two 1.5-Ohm resistors in series. It is unclear
why this modification was done to some G08-003 deflection boards (possibly cooling
reasons?).
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Two resistors hacked onto the back of the current limiting boards: These resistors appear
on Issue 2 and Issue 3 deflection boards for the most part. On both of the current limiting
boards, the trace for pin 1 is cut near the top connector and a 0.2-Ohm 5W resistor is
inserted (i.e., the traces are cut and hooked back together via the resistor). The trace for pin
2 of the connector is also cut near the top, and a 100-Ohm resistor goes from pin 2 to the
BOTTOM CONNECTOR “pin 1” (connecting with the other end of the 0.2-Ohm resistor).
Pin 2 (top) is then jumpered down to the collector of Q704. These resistors are in the
transistor #1 circuit. On issues 5 deflection boards, you will find thesse resistors missing,
but there will be 100-ohm resistors on the deflection board transistor harness across the
terminals of transistor #1.
This resistor ‘hack’ is detailed from an Issue 2 deflection board with an issue 2 screen on
the bottom, and no cut traces on the bottom of the PCB as usually seen on most deflection
boards. I think when this hack is used, the bottom of the PCBs did not have to be cut.
Defection Transistors And Heat Sink
When looking at the back of the monitor, the deflection transistors and associated heatsink is on the
right, mounted to the metal frame. This metal box is a heat sink that holds two pairs of deflection
transistors mounted on opposite sides. A cooling fan is mounted such that it blows air into the heat
sink. The function of this part is to provide cooling of the deflection transistors.
The deflection transistors for the G08-001 are listed in the schematics as MJ15003 and MJ15004.
These transistors were replaced with the more heavy-duty 2N6529 transistors in the G08-003
model. Unfortunately, the 2N6529 transistors have been discontinued, making these beasts difficult
to find.
If you are working on a G08-001 monitor, be VERY careful. The original G08-001 design used the
MJ15003/MJ15004 in a push-pull combination - one NPN and one PNP. The later models of the
G08 used the 2N6259 design where BOTH outputs were NPN. The driver circuit is quite different
between the two models. Be certain you know which monitor you are working on!
Rodger Boots had the following to say about the 2N6259 transistors:
“There is nothing wrong with the 2N6259 and you are going to be hard pressed to find a better part.
Just because the NTE388 LOOKS to be a better part doesn’t tell the whole story. There is not much
out there that has better secondary breakdown characteristics than a 2N6259, but you will never tell